1. Field of the Invention
This invention relates to a process for producing a piperidine derivative and to a stabilized resin composition containing said derivative. More particularly, this invention relates to a process for producing a piperidine derivative represented by the general formula (III) ##STR2## wherein R.sub.1 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; R.sub.2 is a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; and R.sub.3 and R.sub.4 is each independently an alkyl group having 1 to 12 carbon atoms,
and to a resin composition containing said piperidine derivative which has extremely excellent stability not only to heat and oxidation but also to light.
2. Description of the Prior Art
The piperidine derivative represented by the above-mentioned general formula (III) which is an object of this invention, is known to be useful as a light stabilizer for high molecular substances such as plastics, rubbers and fibers.
There has already been known as a process for producing the piperidine derivative represented by the general formula (III) a process which comprises reacting 4-amino-2,2,6,6-tetramethylpiperidine (in the general formula (I) which will be shown later, R.sub.1 and R.sub.2 are each H) with .alpha.-bromo-.alpha.,.alpha.-dimethyl-N-2,2,6,6-tetramethyl-4-piperi dinylacetamide (Japanese Patent Application Kokai (Laid-Open) No. 176939/82).
However, the above known process requires an extremely special raw material, such as .alpha.-bromo-.alpha.,.alpha.-dimethyl-N-2,2,6,6-tetramethyl-4-piperidinyl acetamide, and further gives a low yield of intended product as low as 69%, so that it can hardly be deemed as an industrially satisfactory process for production.
Under these circumstances, the present inventors have made intensive studies to find an industrially advantageous process for producing the piperidine derivative represented by the general formula (III). As a result, it has been found that the intended product can be obtained selectively and without requiring the special raw material, .alpha.-bromo-.alpha.,.alpha.-dialkyl-N-2,2,6,6-tetramethyl-4-piperidinyla cetamide, by reacting a piperidine represented by the general formula (I) shown later and a ketone in the presence of chloroform, alkali and in the presence or absence of a phase transfer catalyst, and thus the present invention has been accomplished.
In the meantime, it is well known that such resins as polyethylene, polypropylene, polyvinyl chloride, polyurethane and ABS resin deteriorate by the action of heat, light and oxygen and undergo marked decrease of mechanical properties accompanied by such phenomena as softening, brittleness, surface crazing and discoloration.
It has been already known for the purpose of preventing such deterioration caused by heat and oxidation to use various kinds of phenol-type compounds such as 2,6-di-t-butyl-4-methylphenol and tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate; for the purpose of further improving the oxidation preventing property to use sulfur-containing compounds such as dilauryl thiodipropionate and pentaerythritol tetrakis(3-dodecylthiopropionate) in combination with said phenol-type antioxidant; and further for the purpose of preventing deterioration by light to use jointly light stabilizers including, for example, benzophenone compounds such as 2-hydroxy-4-n-octoxy-benzophenone, benzotriazole compounds such as 2-(2-hydroxy-3-t-butyl-5-methylphenyl)-5-chloro-benzotriazole and 2-(2-hydroxy-3,5-dipentylphenyl)benzotriazole, cyanoacrylate compounds such as 2-cyano-3,3-diphenylacrylate, Ni-containing compounds such as Ni salt of bis(3,5-di-t-butyl-4hydroxybenzylphosphoric acid) monoethyl ester, and hindered piperidine compounds such as 4-benzoyloxy2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl4-piperidyl) sebacate, and a reaction product of N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexylenediamine with 2,4-dichloro-6-t-octylamino-l,3,5-triazine.
However, even in stabilized resin compositions obtained by using these known stabilizers in combination, the requirements for heat resistance, oxidation resistance and light resistance are not met simultaneously.
For example, when a phenol-type compound and a sulfur-containing compound are used as antioxidants, and a benzophenone compound, benzotriazole compound, cyanoacrylate compound, Ni-containing compounds, or the like is used jointly as a light stabilizer, the resulting products are not fully satisfactory in their light resistance. Further, in cases where hindered piperidine compounds commonly used as a light stabilizer are employed, when a sulfur-containing stabilizer is used in combination therewith, there occurs, presumably owing to antagonism, a serious problem that the excellent light-stabilizing effect inherent to the hindered piperidine compounds is lowered extremely. Consequently, selection have to be made between either to use jointly phenol-type stabilizers alone without using sulfur-containing stabilizer to enhance the light resistance at the sacrifice of the resistance to heat and oxidation or alternatively to use also sulfur-containing stabilizers together to enhance the resistance to heat and oxidation at the sacrifice of the light resistance. Thus, even stabilizer systems using a hindered piperidine compound in combination cannot give fully satisfactory resistances to heat, oxidation and light simultaneously.
The present inventors have made intensive studies to solve these problems and resultantly found that the requirements for heat resistance, oxidation resistance and light resistance can be satisfied simultaneously by using a specified piperidine derivative in combination with a sulfur-containing antioxidant and a phenol-type antioxidant without extreme lowering of light resistance as experienced in combinations of various conventional hindered piperidine compounds with sulfur-containing antioxidants, and thus accomplished this invention.